Deep drawing steels containing chromium



Patented Mar. 26, 1946 DEEP DRAWING STEELS CONTAINING CHROMIUM I I Walter Crafts and Cecil G. Chadwick, Niagara Falls, N. Y., assignorsto Electro Metallurgical Company, a corporation of West Virginia No Drawing. Appllcation'December 1, 1942,

I Serial No. 467,552

4 Claims. (Cl. 75 -126) The invention relates to deep drawing steels, to

deep drawn articles made therefrom.

Deep drawing steels of the low carbon, alumi hum-killed type are currently employed in large quantity by industry. However, not all low carbon fully killed steels are satisfactory for deep drawing purposes. For example, silicon-killed steels are generally less satisfactory than aluminum-killed steels, due to the hardening effect of the silicon addition. .In fact, hardening agents have not been considered helpful in developing deep drawing properties. a

The present invention is based uponthe. discovery that chromium, normally considered a hardening agent for carbon steels, may be used to deoxidize low-carbon steel, that steel so deoxidized has good deep drawing properties, and that deep drawn articleswith an excellent surface finish maybe made therefrom. Heretofore, a deoxidizing .addition'of aluminum has been regarded as a .means. of greatly improving the deep drawing properties of low-carbon steels. On the other hand, chromium has been regarded as not enhancing the deep drawing qualities of low carbon However, in .the present invention chrosteels. mium is used as the deoxidizing agent in the steel and no aluminum or other deoxidizer (except for incidental manganese) isemployed in its manufacture. I

It is accordingly a primary object of the present invention to provide a steel having good deep drawing properties-in which chromium isemployed as a deoxidizing agent. Another object is to provide deep drawn articles having smooth surface characteristics. A further object is to provide a deep drawing steel deoxidized with chromium, which steel has auniform grain size, and physical properties comparable to plain, aluminum-killed deep drawing steels.

- The invention, in its broader aspect, comprises deep drawing steels or articles made therefrom containing between 0.01% and 0.20% carbon, 0.20% to 2% chromium, 0.10% to 1% manganese,

remainder iron and-incidental impurities, such' such for example as ferrochromium, in'an amount suffi'cient t'o deoxidize the melt but insufilcient to leave a residual chromium content greater than 2%, preferably no greater than 1.5%,. casting the steel melt, rollingthe solidified steel to sheet and subjecting the sheet to a pressing operation {to form a deep drawn article.

Due to the existence of many external factors which enter into deep drawing operations, there is no single standard test which can be ,directly interpreted in terms of commercial-deep 'drawing properties. Among the variables encountered inthe deep drawing of steel are the typeof lubricant employed, thedie construction, therate o'f draw, and the surface finish required on thefinal deep drawn article. There are, however, certain physical properties, determinable by simple testing, whichare accepted as indicia of the relative deep drawing characteristics of steels. Ingeneral, these properties are low yield point, moderately low tensile strengthand hardness, good elongation as measured .by percentage elongation in tensile test, depth of cup in cupping test, and substantial-freedom from aging effects.

l The excellent properties obtained by utilizing chromium asthe deoxidizing agent for low carbon steels is shown in Tables A and B in which Table ment of the invention, the upper limit of carbon .hours in an air atmosphere.

.A sets forth the compositions of the steels and Table B the physical properties. The steels of the series were all deoxidized in the furnace, crossrolled to form sheets 0.05 inch in thickness, sand-1 blasted and packannealed. After annealing, the sheets were pickled and cold-rolled to 0.04inch in thickness. The cold-rolled sheets were then annealed at the temperatures indicated in Table B, pickled, and finally given a cold roll pinch pass equivalent totwo per cent reduction. One set of specimens was tested after-the foregoing treatment. 'mens was tested afterthe foregoing treatment plus an accelerated aging treatment that comprised heating the specimens at 200 C. for 24 A visible oxide formed on the specimens due to the aging treatment, which oxide was not removed prior to testing the specimens.

In Table B, Y. P." means yield point in pounds per square inch; '1'. S. means tensile strength in pounds per square inch; El means per centage elongation in a gauge length of two inches; "Hardness R B means the hardness value on the Rockwell B scale; Erichsen means the greatest depth of indentation, measured in millimeters, made in the Erichsen cupping test ing the melt with chromium in any desired form, before incipient cracking of the sheet.

A corresponding set of annealed s'peci Physical properties containing between 0.01%- and0'.20'%- carbon, be- I tween 0.10% and 1%v manganese, between. 0.20% and 2% chromium, remainder ironand incidental than. a steel containingpver 0.07 of phosphorus,

impurities; said steel being. freev from deoxidizing elements}. and deoxidation products thereof, other than saidichromiumand manganese. 7

2.. Deepdrawing, chromium-killed steel other than a steel containing over 0.07% phosphorusf containing between 0.01% and 0.10% carbon, between 0.10% and 0.60% manganese, between 0 .25% and 1.50% chromium, remainder'iron and incidental impurities, said chromium' addition Hardliael Heat tree ant aitereold P. E] I .Enchsen A l) 42,200- 35' 44 I 11.5 1) and aged.... 1 44, 700 31. 5 48 9. 7 2) 50,100 31 53 11.6 e V 2; 000 50,000 32 57 I 9.3 (2 000 46,500 31.5 36 11.7 Annealed (2) and aged- 46,000 36.5 52 9.7

ealed (2) 250 '45, 450 37 33' 12.3 Annealed 2; and aged--. 32,100 47,100 36.5 49 11.4 Annealed 2 L.. ,800 '51, 750 28 37 10.7 Annealed 2) and aged- 30,000 52,000v 24 5s 10:2

I Annealed (1)=710 C.iurnace cool.

. Annealed (2)=925 C.iu'rnaee cool.

' Aged=200 C.'24 hours-air cool- 1 In thetabl'es, steel No. 1 is a low carbon al'uminurn-killed steel of typical physical properties, such as is currently employed inf industry for deep drawing purposes. Steels Nos. 2, 3, 4 and 5 are low carbon steels, containingano' aluminum and very low silicon, which. have been deoxidized withvarious amounts of chromium. As indicat-- ed by these data, chromium when-added alone p .for purposes of 'deoxidati'on permits the produc- 1 .tion of steels of excellent'd'eep drawing characteristics; The steels are further characterized by r a'uniform small grain size; when the chromium-deoxidized steels of the present invention'are rolled into sheet and "pressed into final deep drawn shape the' surface so produced is smooth 1 and typical of material of fairly small and uni- 'form' grain size. There is a defintieincrease in surface smoothness in the drawn areas as the steel containing over 0.07% phosphorus; but, as indicated hereinabove, this invention does not contemplate steels containing impurities in amounts more than normal in low carbon steel of good quality. 7

We claim: 1

*1. Deep drawing chromium-killed steel other,

tion products. thereof, other than. said chromium and manganese.

' 3. An article, deep drawn'to requisite shape and composed 'of a chromium-killed steel other than'a steel containing over 0 .07%: phosphorus, containing between 0.01% and. 0.20% carbon, bee

tween 0.10%; and 1% manganese, betweenv 0 .20% and 2% chromium, remainder iron and inc-idemtal impurities, said article being characterized by the smoothness of surface in the. drawn areas and the uniform small grain size of the steeliof which it is composed; said steel being free from deoxidizing elements, and deoxidation products thereof, other than said. chromium and mai'iga nesc. 1

4. Ari-article, deep drawn to requisite shape.v g

and composed of a chromium-killedsteel other than a'steel containing over 0.07% phosphorus,

containing between 0.01% and 0.10% carbon,be

tween 0.10% and 0.60%. manganese, between 0.25% and 1.50% chromium, remainder iron and incidentaI impurities, said article being characterized by the smoothness of surface. in the drawn manganese. I V

-WALTER CRAFTSQ CECIL o. oHanwrcK; 

